#[derive(Tree, Default)]
pub struct Settings {
    lcd_size: [u8; 2],
    #[tree(depth=3)]
    msgs: [Option<Msg>; 12]
}


const fn const_packed(u: usize) -> Packed {
    match Packed::new(u) {
        Some(p) => p,
        None => panic!("non-zero key required")
    }
}

pub const SIZE: Packed = const_packed(0b01);
pub const MSG_0: Packed = const_packed(0b1_0000_1);
pub const MSG_1: Packed = const_packed(0b1_0001_1);